Dungeons & Dragons 5e Element 133 Class Feature: Battle Alchemist: Weapon OIls

You can coat your weapon with alchemical oils enhancing its powers. As a free action on your turn, you can coat a weapon or piece of ammunition with a oil that enhances the next attack you make on this turn. On a hit, you deal additional damage equal 1d6.

The damage type depends on the type of oil created. When you finish a long rest, you can create a number of oils equal to your proficiency bonus + INT mod. When you create an oil, you decide the damage type for each, from the following list: acid, cold, fire or poison. A oil created loses the effect after 24 hours.

If a creature other than you tries to use the oil, it must use its bonus action to coat a weapon with it.